/*
 * Copyright 2012-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.boot.web.servlet;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Set;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
import org.springframework.context.annotation.ScannedGenericBeanDefinition;
import org.springframework.web.context.WebApplicationContext;

/**
 * {@link BeanFactoryPostProcessor} that registers beans for Servlet components found via
 * package scanning.
 *
 * @author Andy Wilkinson
 * @see ServletComponentScan
 * @see ServletComponentScanRegistrar
 */
class ServletComponentRegisteringPostProcessor implements BeanFactoryPostProcessor, ApplicationContextAware
{

    private static final List<ServletComponentHandler> HANDLERS;

    static
    {
        List<ServletComponentHandler> handlers = new ArrayList<ServletComponentHandler>();
        handlers.add(new WebServletHandler());
        handlers.add(new WebFilterHandler());
        handlers.add(new WebListenerHandler());
        HANDLERS = Collections.unmodifiableList(handlers);
    }

    private final Set<String> packagesToScan;

    private ApplicationContext applicationContext;

    ServletComponentRegisteringPostProcessor(Set<String> packagesToScan)
    {
        this.packagesToScan = packagesToScan;
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException
    {
        if (isRunningInEmbeddedContainer())
        {
            ClassPathScanningCandidateComponentProvider componentProvider = createComponentProvider();
            for (String packageToScan : this.packagesToScan)
            {
                scanPackage(componentProvider, packageToScan);
            }
        }
    }

    private void scanPackage(ClassPathScanningCandidateComponentProvider componentProvider, String packageToScan)
    {
        for (BeanDefinition candidate : componentProvider.findCandidateComponents(packageToScan))
        {
            if (candidate instanceof ScannedGenericBeanDefinition)
            {
                for (ServletComponentHandler handler : HANDLERS)
                {
                    handler.handle(((ScannedGenericBeanDefinition) candidate),
                                   (BeanDefinitionRegistry) this.applicationContext);
                }
            }
        }
    }

    private boolean isRunningInEmbeddedContainer()
    {
        return this.applicationContext instanceof WebApplicationContext &&
                ((WebApplicationContext) this.applicationContext).getServletContext() == null;
    }

    private ClassPathScanningCandidateComponentProvider createComponentProvider()
    {
        ClassPathScanningCandidateComponentProvider componentProvider =
                new ClassPathScanningCandidateComponentProvider(false);
        componentProvider.setEnvironment(this.applicationContext.getEnvironment());
        componentProvider.setResourceLoader(this.applicationContext);
        for (ServletComponentHandler handler : HANDLERS)
        {
            componentProvider.addIncludeFilter(handler.getTypeFilter());
        }
        return componentProvider;
    }

    Set<String> getPackagesToScan()
    {
        return Collections.unmodifiableSet(this.packagesToScan);
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException
    {
        this.applicationContext = applicationContext;
    }

}
